target/mips: Revert TARGET_PAGE_BITS_VARY

Revert ee3863b9d41 and a08d60bc6c2b.  The logic behind changing
the system page size because of what the Loongson kernel "prefers"
is flawed.

In the Loongson-2E manual, section 5.5, it is clear that the cpu
supports a 4k page size (along with many others).  Similarly for
the Loongson-3 series CPUs, the 4k page size is mentioned in the
section 7.7 (PageMask Register).  Therefore we must continue to
support a 4k page size.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250328175526.368121-2-richard.henderson@linaro.org>
[PMD: Mention Loongson-3 series CPUs]
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

hw/mips/fuloong2e.c

@@ -334,7 +334,6 @@ static void mips_fuloong2e_machine_init(MachineClass *mc)
     mc->default_cpu_type = MIPS_CPU_TYPE_NAME("Loongson-2E");
     mc->default_ram_size = 256 * MiB;
     mc->default_ram_id = "fuloong2e.ram";
-    mc->minimum_page_bits = 14;
     machine_add_audiodev_property(mc);
 }
 

hw/mips/loongson3_virt.c

@@ -677,7 +677,6 @@ static void loongson3v_machine_class_init(ObjectClass *oc, void *data)
     mc->max_cpus = LOONGSON_MAX_VCPUS;
     mc->default_ram_id = "loongson3.highram";
     mc->default_ram_size = 1600 * MiB;
-    mc->minimum_page_bits = 14;
     mc->default_nic = "virtio-net-pci";
 }
 

target/mips/cpu-param.h

@@ -18,12 +18,7 @@
 #  define TARGET_VIRT_ADDR_SPACE_BITS 32
 #endif
 #endif
-#ifdef CONFIG_USER_ONLY
 #define TARGET_PAGE_BITS 12
-#else
-#define TARGET_PAGE_BITS_VARY
-#define TARGET_PAGE_BITS_MIN 12
-#endif
 
 #define TCG_GUEST_DEFAULT_MO (0)
 

target/mips/tcg/system/cp0_helper.c

@@ -877,18 +877,13 @@ void update_pagemask(CPUMIPSState *env, target_ulong arg1, int32_t *pagemask)
     if ((mask >> maskbits) != 0) {
         goto invalid;
     }
-    /* We don't support VTLB entry smaller than target page */
-    if ((maskbits + TARGET_PAGE_BITS_MIN) < TARGET_PAGE_BITS) {
-        goto invalid;
-    }
     env->CP0_PageMask = mask << CP0PM_MASK;
 
     return;
 
 invalid:
     /* When invalid, set to default target page size. */
-    mask = (~TARGET_PAGE_MASK >> TARGET_PAGE_BITS_MIN);
-    env->CP0_PageMask = mask << CP0PM_MASK;
+    env->CP0_PageMask = 0;
 }
 
 void helper_mtc0_pagemask(CPUMIPSState *env, target_ulong arg1)

target/mips/tcg/system/tlb_helper.c

@@ -875,7 +875,7 @@ refill:
             break;
         }
     }
-    pw_pagemask = m >> TARGET_PAGE_BITS_MIN;
+    pw_pagemask = m >> TARGET_PAGE_BITS;
     update_pagemask(env, pw_pagemask << CP0PM_MASK, &pw_pagemask);
     pw_entryhi = (address & ~0x1fff) | (env->CP0_EntryHi & 0xFF);
     {